diff --git a/docs/LangRef.html b/docs/LangRef.html
index 893876620a4..ab9f1caae69 100644
--- a/docs/LangRef.html
+++ b/docs/LangRef.html
@@ -1017,8 +1017,9 @@ declare signext i8 @returns_signed_char()
 <dl>
   <dt><tt><b>zeroext</b></tt></dt>
   <dd>This indicates to the code generator that the parameter or return value
-      should be zero-extended to a 32-bit value by the caller (for a parameter)
-      or the callee (for a return value).</dd>
+      should be zero-extended to the extent required by the target's ABI (which
+      is usually 32-bits, but is 8-bits for a i1 on x86-64) by the caller (for a
+      parameter) or the callee (for a return value).</dd>
 
   <dt><tt><b>signext</b></tt></dt>
   <dd>This indicates to the code generator that the parameter or return value
diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index 618ed548947..f257b035b8f 100644
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -1287,6 +1287,17 @@ public:
     return false;
   }
 
+  /// getTypeForExtendedInteger - Return the type that should be used to zero or
+  /// sign extend a zeroext/signext integer argument or return value.
+  /// FIXME: Most C calling convention requires the return type to be promoted,
+  /// but this is not true all the time, e.g. i1 on x86-64. It is also not
+  /// necessary for non-C calling conventions. The frontend should handle this
+  /// and include all of the necessary information.
+  virtual MVT
+  getTypeForExtendedInteger(EVT VT, ISD::NodeType ExtendKind) const {
+    return MVT::i32;
+  }
+
   /// LowerOperationWrapper - This callback is invoked by the type legalizer
   /// to legalize nodes with an illegal operand type but legal result types.
   /// It replaces the LowerOperation callback in the type Legalizer.
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index aa7009ac395..55483188355 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1128,12 +1128,9 @@ void SelectionDAGBuilder::visitRet(const ReturnInst &I) {
         else if (F->paramHasAttr(0, Attribute::ZExt))
           ExtendKind = ISD::ZERO_EXTEND;
 
-        // FIXME: C calling convention requires the return type to be promoted
-        // to at least 32-bit. But this is not necessary for non-C calling
-        // conventions. The frontend should mark functions whose return values
-        // require promoting with signext or zeroext attributes.
         if (ExtendKind != ISD::ANY_EXTEND && VT.isInteger()) {
-          EVT MinVT = TLI.getRegisterType(*DAG.getContext(), MVT::i32);
+          MVT ReturnMVT = TLI.getTypeForExtendedInteger(VT, ExtendKind);
+          EVT MinVT = TLI.getRegisterType(*DAG.getContext(), ReturnMVT);
           if (VT.bitsLT(MinVT))
             VT = MinVT;
         }
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 910ed2abd1f..c1aa7200bef 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1448,6 +1448,15 @@ bool X86TargetLowering::isUsedByReturnOnly(SDNode *N) const {
   return HasRet;
 }
 
+MVT
+X86TargetLowering::getTypeForExtendedInteger(EVT VT,
+                                             ISD::NodeType ExtendKind) const {
+  // TODO: Is this also valid on 32-bit?
+  if (Subtarget->is64Bit() && VT == MVT::i1 && ExtendKind == ISD::ZERO_EXTEND)
+    return MVT::i8;
+  return MVT::i32;
+}
+
 /// LowerCallResult - Lower the result values of a call into the
 /// appropriate copies out of appropriate physical registers.
 ///
diff --git a/lib/Target/X86/X86ISelLowering.h b/lib/Target/X86/X86ISelLowering.h
index 551884b18e4..0857c594b4f 100644
--- a/lib/Target/X86/X86ISelLowering.h
+++ b/lib/Target/X86/X86ISelLowering.h
@@ -843,6 +843,9 @@ namespace llvm {
 
     virtual bool isUsedByReturnOnly(SDNode *N) const;
 
+    virtual MVT
+    getTypeForExtendedInteger(EVT VT, ISD::NodeType ExtendKind) const;
+
     virtual bool
       CanLowerReturn(CallingConv::ID CallConv, bool isVarArg,
                      const SmallVectorImpl<ISD::OutputArg> &Outs,
diff --git a/test/CodeGen/X86/bool-zext.ll b/test/CodeGen/X86/bool-zext.ll
index 67168d4bf04..d2c30c64f23 100644
--- a/test/CodeGen/X86/bool-zext.ll
+++ b/test/CodeGen/X86/bool-zext.ll
@@ -6,7 +6,7 @@
 define void @bar1(i1 zeroext %v1) nounwind ssp {
 entry:
   %conv = zext i1 %v1 to i32
-  %call = tail call i32 (...)* @foo(i32 %conv) nounwind
+  %call = tail call i32 (...)* @foo1(i32 %conv) nounwind
   ret void
 }
 
@@ -16,8 +16,20 @@ entry:
 define void @bar2(i8 zeroext %v1) nounwind ssp {
 entry:
   %conv = zext i8 %v1 to i32
-  %call = tail call i32 (...)* @foo(i32 %conv) nounwind
+  %call = tail call i32 (...)* @foo1(i32 %conv) nounwind
   ret void
 }
 
-declare i32 @foo(...)
+; CHECK: @bar3
+; CHECK: callq
+; CHECK-NOT: movzbl
+; CHECK-NOT: and
+; CHECK: ret
+define zeroext i1 @bar3() nounwind ssp {
+entry:
+  %call = call i1 @foo2() nounwind
+  ret i1 %call
+}
+
+declare i32 @foo1(...)
+declare zeroext i1 @foo2()